LED backlight system for LCD displays

ABSTRACT

A LCD system including multiple light sources optically coupled through different light entry regions to at least one waveguide element positioned to backlight a LCD panel. A LCD system including multiple light sources coupled to light entry regions of two or more waveguides comprising a waveguide system positioned to backlight a LCD panel. Waveguides of various configurations and promoting even lighting of associated LCD panels are provided. Resulting LCD systems enable uniformly lit panels having diagonal measurements in excess of 12 to 14 inches, but the invention is not limited to panels of any particular size.

STATEMENT OF RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 12/983,684filed on Jan. 3, 2011, which is a divisional application of U.S. patentapplication Ser. No. 11/829,912 filed on Jul. 29, 2007, and issuing asU.S. Pat. No. 7,872,705 on Jan. 18, 2011. Such applications are herebyincorporated by reference as if set forth fully herein, for allpurposes, and priority of such applications is hereby claimed under 35U.S.C. 120.

TECHNICAL FIELD

The invention relates generally to liquid crystal displays and, morespecifically, to liquid crystal displays having enhanced lightinguniformity.

BACKGROUND

Traditional display panels, such as cathode ray tube (CRT) displays arebeing replaced by more advanced alternatives, such as liquid crystaldisplays (LCDs) and plasma displays. These newer display technologiesoffer various advantages over traditional CRT technology, includingreduced weight; thinner profile; superior color, contrast and brightnessin the resulting display; and reduced power consumption.

LCDs typically include an array of pixels arranged in front of a lightsource, lighting panel, or reflector. Each pixel includes a layer ofliquid crystal material, and two filters, with one filter serving topolarize light horizontally and the other filter serving to polarizelight vertically. A reflective LCD has a reflective layer (such as amirror) behind the pixels and is lit by either a frontlight or byambient light. A transmissive LCD is lit by a backlight, in anarrangement where the pixels are arranged in front of a light source andlight from the light source is transmitted through the pixels to thefront of the LCD or the viewing area, resulting in a “lit” pixel. Lightsources for backlighting may include electroluminescent panels/foils(ELs), cold cathode fluorescent lamps (CCFLs), hot cathode fluorescentlamps (HCFLs) External Electrode Fluorescent Lamps (EEFLs), traditionalincandescent light bulbs, or light emitting diodes (LEDs). Highintensity discharge lamps (HIDs) may also be used in certainbacklighting applications.

When LEDs are utilized as light sources for transmissive LCDbacklighting, they may be traditional or side view LEDs. Side view LEDsare also known as “side emitting LEDs” or “side looker LEDs.” A sideview LED is a packaged LED that emits light parallel to the plane of thesurface to which the package is mounted. Compared to traditional LEDpackages, side view LED packages are thinner and typically lessexpensive to manufacture. A typical side view LED package has dimensionsof about 1.5 mm by about 0.5-0.7 mm, but such dimensions may vary. Owingat least in part to their small size, side view LED packages havelimited current handling capabilities, thus limiting their emissions. Asa result, a single side view LED package typically has less outputcapability than a traditional LED package. Whether accidentally ordeliberately, practitioners often “overcurrent” side view LEDs toachieve greater output, which can lead to overheating and failure of adevice incorporating such LEDs.

Current LED lighting techniques for transmissive LCDs include eitherdirect backlighting or backlighting by edge illumination. While abacklight will light the pixels from the backside, that light may comefrom directly behind the center of the pixels (direct backlighting) orfrom behind the sides of the pixels (backlighting by edge illumination).While both techniques are recognized as backlighting, directbacklighting refers to illumination directed axially (centrally) throughthe backside of pixels. In contrast, edge illumination refers to anarrangement where the light source is located along an edge of a LCDsystem and lights the pixels from the side. Edge illumination may occuralong the side edges of the LCD, the top edge, or the bottom edge.Backlighting of transmissive LCDs may utilize a waveguide to spread thelight to an entire LCD panel, with such waveguide having a single entryfor light and transmitting the light by internal reflection to be spreadover a desired area.

A traditionally LED backlit LCD may include a layered system thatincludes an array of red, green and blue LEDs positioned on a panel orarray of tiles. The panel or tiles include a reflective surface or layerarranged so that light is reflected in the desired direction toward adiffusion layer that diffuses the light provided from the LED backlightand reflects some of the light back toward the reflective surface orlayer, thereby functioning to mix the light and improve the lightuniformity (“recycling effect”). A brightness enhancement film and/orcollimating layer over the reflective layer or surface and the diffusionlayer provides light to the LCD panel layers in a more optimal fashionand also acts with the reflective layer or surface and the diffusionlayer to enhance the recycling effect Depending on the embodiment,additional or less layers can be utilized as is understood by one ofskill in the art. Such a backlight system may also include thermallayers below the LEDs for thermal management. As such, as is understoodby one of skill in the art, the LED backlight system provides uniformwhite light to the LCD panels, which typically include a shutter layerand red, green and blue color filters.

The above-described traditionally lit screens have several inherentlimitations. In the context of direct backlighting with a LED, atraditional LED package emits light directly at (i.e., through) a LCDscreen. In order to light the entire screen, the LED must operate athigh power and be very thick if utilized without a waveguide.Accordingly, the thickness of the resulting LCD system (television,monitor, etc.) is also increased. Modern consumers, however, desirethinner profile systems with thicknesses as small as a few inches.Accordingly, thick LCD systems are not commercially desirable.Additionally, use of high powered traditional LED package without awaveguide may create a “headlight effect” also known as a “hot spot” onthe panel, causing a detrimental lack of light uniformity.

With regard to edge illumination, in which a waveguide is used to spreadthe light emission of a side view LED package disposed on an edge of theLCD, the resulting screen size is limited. As indicated previously,light emission characteristics of side view LED packages are reduced incomparison to traditional LED packages, with such limitation due totheir size and current handling capabilities. As a result of the lowerlight emission, and the single entry for light in the waveguide, one ormore portions (i.e., typically the center) of a side view LED-lightedLCD screen may not be lit if the screen is relatively large in size. LCDscreens illuminated with side view LED packages and having acceptablyuniform illumination characteristics are currently limited to screens ofabout 12 to 14 inches (diagonal) in size.

Accordingly, a need exists in the art for backlit LCD displays anddisplay systems that are light in weight, have a thin profile, thatenable use of large screens, and that are uniformly lit over the entiredisplay with superior color and contrast. These and other needs areaddressed with devices and systems according to embodiments of thepresent invention.

SUMMARY

The present invention provides improved liquid crystal display systemsand methods of using the same.

In one aspect, the invention relates to a liquid crystal display (LCD)system including: a) a liquid crystal display panel; b) at least onewaveguide element comprising a plurality of light entry regions; c) afirst light-emitting source positioned to emit light into the at leastone waveguide element at a first light entry region of the plurality oflight entry regions; and d) at least a second light-emitting sourcepositioned (i) to emit light into the at least one waveguide element ata second light entry region of the plurality of light entry regions or(ii) to emit direct backlight onto the liquid crystal display panel;wherein the first light-emitting source and the second light-emittersource are arranged to light different regions of the liquid crystaldisplay panel.

In another aspect, the invention relates to a waveguide systemcomprising: a) a first waveguide element comprising at least one firstlight entry region; b) a first light-emitting source positioned to emitlight into the first waveguide element at the first light entry region;c) at least a second waveguide element comprising at least one secondlight entry region; and d) at least a second light-emitting sourcepositioned to emit light into the at least a second waveguide element atthe at least one second light entry region. Embodiments of the inventionalso provide LCD systems utilizing waveguide systems as described herein

In another aspect, the invention relates to a liquid crystal display(LCD) system comprising: a) a LCD panel having a peripheral region andan inner region; b) at least one first waveguide element comprising atleast one first light entry region at an edge of said LCD panel andarranged to backlight the peripheral region of said LCD panel; c) atleast one first light-emitting diode source positioned to emit lightinto said at least one first light entry region; and d) at least asecond light-emitting diode source positioned to emit light forbacklighting of the inner region of said LCD panel.

In another aspect, the invention relates to a liquid crystal display(LCD) system comprising: a) a LCD panel; b) at least one waveguideelement comprising at least one light entry region, wherein the at leastone light entry region comprises an extension of the at least onewaveguide element that is non-coplanar with a principal plane of the atleast one waveguide element; c) a first light-emitting source positionedto emit light into the at least one waveguide element at the at leastone light entry region; and d) at least a second light-emitting sourcepositioned to emit direct backlight onto the LCD panel or positioned toemit light into the at least one waveguide element along an edgethereof.

Methods utilizing waveguide elements and LCD systems are also providedin certain aspects of the invention.

In a further aspect, any of the foregoing aspects may be combined foradditional advantage.

These aspects and other aspects and advantages of the invention will beapparent to one skilled in the art upon review of the ensuing disclosureand accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic front view illustration of at least a portion ofan exemplary LCD system including a waveguide element with edgeillumination from two side edges, utilizing a plurality of LEDs arrangedin strips as light sources according to one embodiment of the invention.

FIG. 1B is a schematic perspective view illustration of the exemplaryLCD system of FIG. 1A.

FIG. 1C is a schematic perspective view of the multi-LED strip lightsource of FIG. 1A and 1B, disposed adjacent to a waveguide.

FIG. 1D is a perspective view of a television or computer monitorincluding a LCD system according to FIG. 1B.

FIG. 2 is a schematic perspective view illustration of at least aportion of an exemplary LCD system including a waveguide element withangled extensions to receive light from a plurality of LEDs arranged instrips, according to one embodiment of the invention.

FIG. 3 is a schematic view illustration of at least a portion of anexemplary LCD system including a waveguide element with multipleextensions curved toward a principal plane of the waveguide elementaccording to one embodiment of the invention.

FIG. 4 is a schematic perspective view illustration of an exemplary LCDsystem including a waveguide element subject to both backlighting by aplurality of LEDs arranged in strips behind the LCD screen, and sidebacklighting by a plurality of LEDs arranged in strips along at leastone side edge of the system according to one embodiment of theinvention.

FIG. 5 is a schematic illustration of a plurality of LEDs arranged in astrip for use in a light-emitting source in a LCD system according toone embodiment of the invention.

FIG. 6A is a schematic front view illustration of a lit LCD screen,lighted by a waveguide system containing two waveguides, according toone embodiment of the invention.

FIG. 6B is a cross-sectional view illustration of the LCD screen of FIG.6A and at least a portion of an associated waveguide system arranged tolight the LCD screen.

FIG. 7A is a schematic front view illustration of a lit LCD screen,lighted by a waveguide system containing three waveguides, according toone embodiment of the invention.

FIG. 7B is a cross-sectional view illustration of the LCD screen of FIG.7A and at least a portion of an associated waveguide system arranged tolight the LCD screen according to one embodiment of the invention.

FIG. 8A is a schematic front view illustration of a lit LCD screen,lighted by a waveguide system containing four waveguides, according toone embodiment of the invention.

FIGS. 8B and 8C are cross-sectional view illustrations of LCD screen ofFIG. 8A and at least a portion of an associated waveguide systemarranged to light the LCD screen, according to one embodiment of theinvention.

FIG. 9A is a schematic front view illustration of a lit LCD screen,lighted by a waveguide system containing four waveguides, according toone embodiment of the invention.

FIG. 9B is a cross-sectional view illustration of the LCD screen of FIG.9A and at least a portion of an associated waveguide system arranged tolight the LCD screen according to one embodiment of the invention.

DETAILED DESCRIPTION

The present invention relates in various aspects to improved LCDsystems. In one embodiment, a LCD system comprises a LCD panel orscreen, at least one waveguide with multiple entry regions for light,and at least two light-emitting sources positioned to emit light intothe at least one waveguide. When the light emitted by the light-emittingsources is optically coupled into the waveguide, the waveguide transmitslight sufficient to light the entire LCD panel or screen of the system.Alternatively, multiple waveguides may be employed, each with at leastone entry region for light and at least one associated light-emittingsource positioned to emit light into the waveguides. With multiplewaveguides, each waveguide may be positioned to light a portion of theLCD panel.

A conventional LCD system generally includes a LCD panel and a lightsource such as a LED optionally coupled to a single waveguide elementhaving a single light entry point. Side view LED packages are desirablefor use in LCD systems, due to their low current usage and small size.Due to concerns of overheating, however, the current that can besupplied to side view LED packages is limited, thus limiting theiremissions. Consequently, the amount of light that can be emitted from asingle side view LED package into a conventional waveguide is alsolimited. Therefore, side view LED packages coupled to single-inputwaveguides are not well-suited for use in backlighting LCD panels havingviewable diagonal measurements larger than approximately 12-14 inches.

Embodiments of the present invention are not so limited, as they providefor uniform backlighting of panels of any desirable size, includingpanels having viewable diagonal measurements larger than about 12inches, without problems such as overheating and creation of “hotspots.” LCD systems embodied in the present invention may include, butare not limited to televisions and computer monitors.

Embodiments of the present invention include single waveguides havingmultiple light entry regions for receiving light from locations otherthan, and/or in addition to, a single edge of the waveguide. Theprovision of light into at least one waveguide from multiple entryregions permits low current side view LED packages, whether alone orwith other types of light sources, to uniformly light a LCD panel orscreen, even if the LCD panel or screen has a viewable surface with adiagonal measurement greater than approximately 12-14 inches.

Embodiments of the present invention also include waveguide systemscomprising multiple waveguides each waveguide having at least a singlelight entry region. Such a waveguide system may be utilized in a LCDsystem, where each waveguide has a transmissive surface that lights aportion of the LCD panel. The provision of light to multiple waveguidespermits use of low current side view LED packages, whether alone or withother types of light sources, to uniformly light the LCD panel.

A LCD system according to the present invention may include any suitabletype of conventional LCD panel or screen. Generally, a LCD panelincludes LCD pixels arranged in front of a light source or reflectivesurface to illuminate the pixels. Furthermore, the LCD may include anLCD shutter panel and/or color filters, such as RGB color filters, asare known to those of skill in the art.

In one embodiment, a LCD system according to the present inventionincludes a transmissive LCD, such that the light is provided to the LCDpanel or screen from behind via at least one waveguide element.Preferably the at least one waveguide element disperses the light in aneven and complete manner, such that the entire panel is lit consistentlyand at a consistent intensity. A single waveguide element may beutilized, or multiple waveguide elements may be utilized with a singleLCD panel. A waveguide element is a device utilized to guide opticalwaves from a light entry region to a transmissive surface or exit regionof the waveguide element. A waveguide element may comprise a hollowstructure with a reflective internal surface; alternatively, a waveguidemay be substantially solid in nature. Glass, quartz, plexiglass, andother optically transmissive materials may be employable in thefabrication of transmissive portions of waveguides, with reflectivematerials such as metals further employed to fabricate reflectiveportions. Other materials such as glass and plastic may be employed tofabricate additional portions of the waveguide. To minimize loss oflight from the waveguide element from an area other than thetransmissive surface or exit region, the waveguide element may also besurrounded in whole or in part by a material such as plastic to reflectany light back into the element. In one embodiment, the waveguideincludes a prism. At least a portion of a waveguide may be substantiallyplanar or tubular in shape, or of any other configuration known to thoseof skill in the art. Total internal reflection is desirable, such thatall of the light supplied to the waveguide element from associated lightsource(s) is transmitted out of the waveguide element via thetransmissive surface. Internal reflection guides the optical waves to atransmissive surface of the waveguide element, which is opticallycoupled to provide light to the LCD screen or panel, such that the LCDpanel or screen may be lit by the transmitted light. A waveguide isgenerally utilized in an arrangement where the LCD panel or screen islocated between the waveguide element and a viewer.

When a single waveguide element is used, the waveguide preferably hasmultiple light entry regions. Additionally, the transmissive surface ofthe waveguide element and the viewable surface of the LCD panel orscreen are preferably of substantially the same size. Optionally, thewaveguide may contain gaps or holes to allow light from a directbacklight to the LCD panel or screen.

Waveguides utilized in LCD systems according to the invention may beutilized in combination, and when multiple waveguides are employed in awaveguide system, each may have one or more light entry regions. Lightenters the one or more light entry regions of a waveguide and istransmitted to the transmissive surface thereof. A transmissive surfaceis preferably substantially flat to conform to a LCD panel. Thistransmissive surface provides backlight to the LCD panel, and is capableof lighting the viewable surface of the LCD panel or screen. In a LCDsystem of the invention, one or more waveguides may be utilized inlighting the LCD panel or screen.

When multiple waveguide elements are used, each waveguide preferably hasat least one light entry region. The combined transmissive surface areaof the waveguide elements is preferably substantially the same as thatof the viewable surface area of the LCD panel or screen. Each waveguideof the group may light a different portion of the LCD panel, or thecombined transmission may light substantially all of the LCD panel. Inanother embodiment, when multiple waveguides are utilized, thewaveguides may be spaced sufficiently to allow light from a directbacklight to the LCD screen or panel or any of the individual waveguidesof the group may contain gaps or holes to allow light from a directbacklight to the LCD panel or screen. When multiple waveguides areemployed, they may abut one another laterally, or at least portionsthereof may be disposed in a front-to-back or layered relationship ifdesired. In one embodiment, multiple upstream waveguides may beoptically coupled to a downstream waveguide to promote easy fabricationand/or enhance uniformity of light distribution.

A light entry region of a waveguide element according to the inventionmay be adapted to receive light from one or more light sources. Lightentry regions may be arranged along any convenient portion of awaveguide element. If a front portion of a waveguide is opticallycoupled to transmit light to a LCD panel or screen, then light entryregions may be disposed along any of a top edge, a first side edge, asecond side edge, a bottom edge, and a back side of the waveguideelement.

A waveguide element of the invention may be also adapted for use with adirect backlight source. As described above, a traditionally backlit LCDsystem includes a layered system which may include a direct backlightand, optionally, thermal layers under the light source, reflectivelayer(s), diffusion layer(s), brightness enhancement film(s) and/orcollimating layer(s). In one embodiment of the invention the waveguideelement of the invention is adapted for use with a direct backlightsource, such that the waveguide element is included within or inaddition to the layered backlight system. Where direct backlighting isprovided in the LCD system of the invention, inclusion and orientationof such layers, films and elements, including one or more waveguideelements, is provided to optimize the direct backlight transmitted tothe LCD panel or screen. In one embodiment a waveguide element isprovided between the direct backlight source and the diffusion layer. Inanother embodiment, the waveguide element serves as a diffusion layer.

Multiple waveguides may form a “waveguide system” such that in oneembodiment, light transmitted from each of the waveguides is coupled toprovide light to the LCD panel or screen of a LCD system. A waveguidesystem in another embodiment may include two or more waveguides arrangedin a layered configuration, where each waveguide provides light to adifferent portion of a LCD panel, such that the entire panel issubstantially illuminated by the waveguide system. Each individualwaveguide within the waveguide system includes one or more light entryregions, to which one or more light sources are optically coupled. Eachwaveguide also includes a transmissive surface or an exit region, wherelight exits the waveguide. A transmissive surface may comprise glass,quartz, or other optically transmissive materials, and may be referredto as a “prismatic” section of the waveguide. Portions of the waveguidenot comprising a transmissive surface may comprise materials withoutprismatic or transmissive properties. The waveguide may also comprise amaterial or be surface treated such that a light shined directly at thewaveguide will enter the waveguide or pass through the waveguide.Optionally, layered waveguides may be alternated with layers ofdiffusers and/or “light shaping” components.

In an exemplary LCD system according to one embodiment of the invention,a waveguide system including two layered waveguides is used, where thefirst waveguide may light a central or interior region of the LCD screenand the second waveguide may light a peripheral or outer region of theLCD screen. FIG. 6A illustrates a LCD screen 42 lit by a two layerwaveguide system according to one embodiment of the invention. On thelighted screen 42, a first waveguide (not shown) is arranged to providelighting to a central portion 45 of the LCD screen 42 and a secondwaveguide (not shown) is arranged to provide lighting to a peripheral orouter section 46 of the LCD screen 42. Each waveguide of the waveguidesystem preferably receives light from at least one different lightsource (not shown). FIG. 6B provides a cross-sectional view of anexemplary waveguide system 41 used to light a LCD screen 42 such asillustrated in FIG. 6A, taken along section lines B-B of FIG. 6A. As canbe seen in FIG. 6B, in the exemplary two waveguide system 41, thewaveguide layers 44A, 44B may be of similar size to one another. Thewaveguides 44A, 44B are positioned in a layered configuration, such thatone waveguide 44A is positioned between the second waveguide 44B and theLCD screen 42. Each waveguide 44A, 44B has a transmissive or prismaticportion 49A, 49B on a major surface that emits light toward the LCDscreen 42. Each waveguide 44A, 44B lights a portion of the LCD screen42, such that the LCD screen 42 is substantially lit. A waveguide systemmay optionally be backed by a minor or white light diffuser 40, and/ormay contain additional diffusers or light shaping components (not shown)between the waveguide layers 44A, 44B.

In one embodiment according to the present invention, a waveguide systemincludes three layered waveguides, with a first waveguide lighting acentral or interior region of the LCD screen, a second waveguidelighting a first portion of a peripheral or exterior region of the LCDscreen, and a third waveguide lighting a second (e.g., remaining)portion of the peripheral or exterior region of the LCD screen. FIG. 7Aillustrates an exemplary lit LCD screen 52 utilizing a three layerwaveguide system 51. On the lighted screen 52, a first waveguide (notshown) is arranged to provide lighting to a first portion 55 along thecenter of the LCD screen 52, a second waveguide (not shown) is arrangedto provide lighting to a second portion 56 along the exterior of the LCDscreen 52 and a third waveguide (not shown) is arranged to providelighting to a third portion 57 along a remaining exterior portion of theLCD screen 52. Each waveguide 54A-54C of the waveguide system preferablyreceives light from at least one different light source (not shown).FIG. 7B provides a cross-sectional view of an exemplary waveguide system51 used to light LCD screen 52 as illustrated in FIG. 7A, taken alongsection lines B-B of FIG. 7A. As can be seen in FIG. 7B, each waveguidelayer 54A-54C of the exemplary three waveguide system 51 may be ofsimilar size. The waveguides 54A-54C are positioned in a layeredconfiguration, such that one waveguide 54A is positioned closest to theLCD screen 52 and the third waveguide 54C is positioned furthest fromthe LCD screen 52, with the second waveguide 54B positioned between thefirst and third waveguides 54A, 54C. Each waveguide 54A-54C has atransmissive or prismatic portion 59A-59C on a major surface thereofthat emits light toward the LCD screen 52. Each waveguide 54A-54C lightsa portion of the LCD screen 52, such that the entire LCD screen 52 issubstantially lit. The waveguide system 51 may optionally be backed by amirror or white light diffuser 50, and/or may contain additionaldiffusers or light shaping components (not shown) between the waveguidelayers 54A-54C.

In another embodiment according to the present invention, four layeredwaveguides are provided. In such an arrangement, the waveguides may eachprovide light to a different portion (e.g., quadrants) of a LCD screen.

FIG. 8A illustrates such an exemplary LCD screen 62 lit by a four layerwaveguide system. On the exemplary lit screen 62, a first waveguide (notshown) is arranged to provide lighting to a first portion 65corresponding to an upper left quadrant of the LCD screen 62, a secondwaveguide (not shown) is arranged to provide lighting to a secondportion 66 corresponding to a lower left quadrant of the LCD screen 62,a third waveguide (not shown) is arranged to provide lighting to a thirdportion 67 corresponding to an upper right quadrant of the LCD screen62, and a fourth waveguide (not shown) is arranged to provide lightingto a fourth portion 68 corresponding to a lower right quadrant of theLCD screen 62. Each waveguide of the waveguide system preferablyreceives light from at least one different light source (not shown).FIG. 8B provides a first cross-sectional view of a waveguide system 61useable to light the LCD screen 62 of FIG. 8A, taken along section linesB-B of FIG. 8A. FIG. 8C provides an alternative cross-sectional view ofa first waveguide system useable to light the LCD screen 62 of FIG. 8A,taken along section lines C-C. As can be seen in FIGS. 8B and 8C, in theexemplary four waveguide system 61, the waveguide layers 64A-64D are ofsimilar size to one another. The waveguides 64A-64D are positioned in alayered configuration, such that a first waveguide 64A is positionedclosest to the LCD screen 61 and a fourth waveguide 64D is positionedfurthest from the LCD screen 61, with a second waveguide 64B and a thirdwaveguide 64C positioned between the first and fourth waveguides 64A,64D. Each waveguide 64A-64D has a transmissive or prismatic portion69A-69D on its surface that emits light toward the LCD screen 62. Eachwaveguide 64A-64D lights a portion of the LCD screen 62, such that theentire LCD screen 62 is substantially lit. The waveguide system 61 isoptionally backed by a mirror or white light diffuser (not shown) andmay contain additional diffusers or light shaping components (not shown)between the waveguide layers 64A-64D.

FIG. 9A illustrates an exemplary LCD screen 72 lit by another four layerwaveguide system. On the exemplary lit screen 72, a first waveguidelights a first portion 75 of the LCD screen 72, a second waveguidelights a second portion 76 of the LCD screen 72, a third waveguidelights a third portion 77 of the LCD screen 72, and a fourth waveguidelights a fourth portion 78 of the LCD screen 72. Each waveguide 74A-74Dof the waveguide system preferably receives light from at least onedifferent light source (not shown). FIG. 9B provides a cross-sectionalview of a waveguide system 71 useable to light the LCD screen 72 of FIG.9A, taken along section lines B-B of FIG. 9A. As can be seen in FIG. 9B,in the exemplary four waveguide system 71, the waveguide layers 74A-74Dare of similar size to one another. The waveguides 74A-74D arepositioned in a layered configuration, such that a first waveguide 74Ais positioned closest to the LCD screen 72 and a fourth waveguide 74D ispositioned furthest from the LCD screen 72, with a second waveguide 74Band a third waveguide 74C positioned between the first and fourthwaveguides 74A, 74D. Each waveguide 74A-74D has a transmissive orprismatic portion 79A-79D on its surface that emits light toward the LCDscreen 72. Each waveguide 74A-74D lights a portion of the LCD screen 72,such that the entire LCD screen 72 is substantially lit. The waveguidesystem 71 is optionally backed by a minor or white light diffuser (notshown) and may contain additional diffusers or light shaping components(not shown) between the waveguide layers 74A-74D.

It is to be understood that the exemplary waveguide systems describedabove are not limited to the particular transmission configurationsprovided herein. Any number of waveguides may be arranged in anyconfiguration such that the transmissive sections of the waveguidesilluminate various sections of a LCD screen. Transmission by thewaveguides in any particular configuration does not have to be evenlydistributed among individual waveguides. The exemplary waveguide systemsset forth above include waveguides of approximately similar size;however, the waveguides of a waveguide system may be of any size, aslong as the resulting transmissive sections of those waveguidesilluminate substantially all of the LCD screen.

As described hereinabove, one or more light sources are opticallycoupled to a waveguide element in various embodiments of the invention.Any number of light sources may be employed to achieve uniform lightingof a LCD panel. While the light sources are optically coupled to emitlight into the light entry regions of the waveguide element, the numberof light entry regions does not limit the number of light sources. Inone embodiment, at least one waveguide element is utilized, including afirst light-emitting source positioned to emit light into a first entryregion of the at least one waveguide element and a second light-emittingsource positioned to emit light into a second entry region of the atleast one waveguide element. Additional light-emitting sources and lightentry regions may be employed.

A light-emitting source may be positioned anywhere within a LCD systemthat allows optical coupling of the light emitted into a light entryregion. Accordingly, light-emitting sources may be located in or along aside region, a top region, a bottom region and/or a rear region of theLCD system. Light-emitting sources may be spaced apart fromcorresponding light entry regions, may be adjacent to correspondinglight entry regions, and/or may be physically coupled to thecorresponding light entry regions. In one embodiment, the light-emittingsources include side view LED packages, the light-emitting sources arearranged to not simultaneously and solely emit light into a top edge anda bottom edge of the waveguide. In such an embodiment, light sources maybe arranged in locations other than both the top and bottom edges of thewaveguide, or light sources arranged along both the top and bottom edgeof a waveguide are supplemented with at least one additional lightsource arranged to emit light into the waveguide from at least one otherlocation.

Optical coupling between a light source and waveguide element mayinclude any of: directing light to one or more recesses defined awaveguide element, embedding a light source in a waveguide element, anddirecting light to at least one edge or surface of a waveguide element.The waveguide element does not need to be uniform in shape and,optionally, may contain one or more extensions oriented in any suitabledirection, such that the light source may be optically coupled to thewaveguide element via the one or more extensions.

As thinner profile LCD systems may be desirable, where waveguideextensions are utilized, they may be optionally oriented in a mannersuch that they are angled, bent, or curved toward a primary plane of thewaveguide element itself and, correspondingly, toward the LCD panel, toachieve a thinner profile system.

In one embodiment, a LCD system may further comprise a light source thatis not optically coupled to emit light into the waveguide. An exemplarysystem includes a light source that directly backlights a LCD panel,supplemented by waveguide-directed light. Light emitted by such abacklight may pass through or around a waveguide or waveguide systemdisposed between the backlight and the LCD panel, in order to transmitlight from the backlight to the LCD panel. In such an embodiment, thebacklight provides light to the LCD panel or screen, which light issupplemented in one or more locations by light transmitted by thewaveguide or waveguide system.

In another embodiment, a LCD system may further comprise a directbacklight source that is optically coupled into the waveguide asunderstood by one of skill in the art. An exemplary system includes alight source that provides light optically coupled into the waveguide,where the light source is positioned directly behind the LCD panel. Suchdirect backlighting may be coupled into the waveguide by any means knownto those of skill in the art. In one embodiment the LED is provided atthe end of a waveguide extension. Such a waveguide extension may beoriented in any manner as more fully described above. Preferably such anextension is short and the backlight is flush with the extension. Inanother embodiment the waveguide comprises such a material or issurface-treated such that a direct backlight shined on the waveguidewill enter the waveguide through the surface and will be opticallycoupled to light provided to the waveguide through additional lightentry sources. In a still further embodiment, the waveguide contains alight entry source in the form of a notch, or groove or otherindentation in the surface of the waveguide, allowing for placement of adirect backlight directly against the waveguide. Light emitted from thedirect backlight can therefore be optically coupled directly into thewaveguide.

Light sources useful in lighting a LCD panel can include any of: a coldcathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL),an electroluminescent panel (ELP), an incandescent light bulb, a lightemitting diode (LED), an organic light emitting diode (OLED), a highintensity discharge (HID) lamp, and any combination of the foregoingsources arranged to provide light in additive or spatially discretearrangement.

Where LEDs are utilized as light sources in embodiments of the presentinvention, such LEDs are preferably embodied in LED packages. Suchpackages may include packaged traditional LEDs that emit light from aside opposite the electrode from which they receive current, and/or maybe packaged side view LEDs (also known as “side emitting LEDs” or“sidelooker LEDs”) that emit light substantially parallel to a plane ofthe surface on which the package is mounted. A “LED package,” as usedherein, preferably includes a substrate, an electrode, a LED chipmounted on or over the substrate and an encapsulant disposed on or overthe LED chip. A LED package may also include any of: a diffuser, areflector, a lens, an electrostatic discharge diode, and/or thermalconduction elements.

A light source in a LCD system of the invention may include a LED thatemits any of white light, blue light, red light, green light, or lightof any desirable wavelength. In one embodiment, a light source includesone or more clusters of red-green-blue (RGB) LEDs. Such clusters may beindependently controlled. In another embodiment, a light source includesa blue LED coated or otherwise covered with phosphors to upconvert bluelight to white light.

Exemplary combinations of light sources of the invention may include:(1) direct backlighting utilizing one or more side view LEDs,supplemented with edge backlighting utilizing one or more side viewLEDs; (2) direct backlighting utilizing one or more traditional LEDs,supplemented with edge backlighting utilizing one or more side viewLEDs; (3) direct backlighting utilizing one or more side view LEDs,supplemented with edge backlighting utilizing one or more traditionalLEDs; (4) direct backlighting utilizing one or more traditional LEDs,supplemented with edge backlighting utilizing one or more traditionalLEDs; and (5) edge backlighting from more than one edge, utilizing oneor more side view LEDs or traditional LEDs, or any combinations thereof.Such combinations may include, but are not limited to, single lightsources including both traditional and side view LEDs. The foregoingcombinations represent mere examples of possible configurations; otherconfigurations may be employed within the scope of the presentinvention.

A single light source may comprise a plurality of LEDs. The LEDs of sucha plurality of LEDs may be arranged in any suitable configuration,whether to enable convenient manufacture, to maximize light emitted intothe light entry regions of the at least one waveguide element, or both.Exemplary arrangements include multiple LED packages arranged in astrip, or a single LED package containing multiple LEDs arranged in astrip. Such a strip may contain two or more LEDs or LED packages.Individual LEDs or LED packages within a single strip may becharacteristically the same as, or different from, other LEDs or LEDpackages in the same strip. LEDs or LED packages in a single strip maybe adapted to emit substantially the same wavelength, or may be adaptedto emit different wavelengths. Additionally, multiple strips may beconnected to one another in any suitable orientation, such as in anend-to-end orientation, or in a side-to-side orientation, in order toyield a single composite light source to emit light into the waveguideelement. Where multiple strips are utilized, each strip may be adaptedto emit light of substantially the same wavelength as other strips, ormay be adapted to emit light of wavelengths different from light otherstrips.

A light source including a strip of LEDs or LED packages may include acircuit board or other common structural support, such that the LEDs maybe electrically connected to one another. The LEDs may be furtherelectrically connected to components adapted to provide uniformperformance of the plurality of LEDs. Such components may include one ormore common control circuits (e.g., integrated circuits or processors)to regulate, for example, power to the LEDs, intensity of the emittedlight, wavelength of the emitted light, and/or other parameters.Additionally, a strip of LEDs may include or be connected to one or morecommon electrostatic discharge (ESD) diodes, providing protection fromvoltage spikes to multiple LEDs within the strip. Moreover, multiplestrips may be subject to control from a single master control circuit orCPU.

FIG. 5 illustrates of an exemplary light source for use in a LCD system,including a plurality of LED packages arranged in a strip 100. In apreferred embodiment, the strip 100 has dimensions of 20 mm×2.5 mm andcontains five or more LED packages 101A-101E, which may be disposed inseries. Optionally, such a strip 100 comprises a circuit board 105including a 2.5 mil thickness FR4 substrate and 1 oz. copper,electroless Nickel Immersion Gold plating, and does not containsoldermask on the back surface. The strip 100 includes a common ESDdiode 102 in electrical communication with the LEDs 101A-101E. Contacts103, 104 may be provided to serve as common electrical inputs for thestrip 100.

It is understood that when a single light source comprises a pluralityof LED packages, any desirable number of LED packages may be provided.Factors affecting the makeup of a single light source may include: thesize of the panel being lit, the desired viewing angle, the entry angleof the light into the light entry region of the waveguide element, thespacing of the individual LED packages, the brightness of the individualLED packages, and the size of the LED packages. In combination, plurallight sources coupled to at least one waveguide utilized in a system asdescribed herein are adapted to uniformly light a LCD panel of anydesired size.

FIG. 1A is a schematic front view illustration of at least a portion ofan exemplary LCD system 1 including a LCD panel 2 and multiple lightsources 3A, 3B. FIG. 1B is a schematic side view illustration of thesystem of FIG. 1A, depicting the LCD panel 2, light sources 3A, 3B andwaveguide element 4. FIG. 1C is a schematic side view illustration of anexemplary light source 3B, comprising a plurality of side view LEDpackages, 6A-6E arranged as a strip on base 7 and emitting light 8,parallel to the plane of base 7, into waveguide 4. FIG. 1D is aperspective view of a television or computer monitor 100 including a LCDsystem according to FIG. 1B, with the LCD panel 2 arranged in theforeground.

FIG. 2 is a schematic perspective view illustration of at least aportion of an exemplary LCD system 11 according to an embodiment of thepresent invention, including a LCD panel 12, waveguide element 14, firstlight source 13, and additional light sources 15A-15D, each coupled tothe waveguide element 14 at the end of waveguide extensions 16A-16D,respectively. In FIG. 2, the first light source 13 provides light to alight entry region located along a lateral edge of the waveguide element14 and additional strips of LED packages 15A-15D are optically coupledto the waveguide element 14 along light entry regions on extensions16A-16D of the waveguide element 14.

FIG. 3 is a schematic perspective view illustration of at least aportion of an exemplary LCD system 21 according to one embodiment of theinvention, the system including a LCD panel 22, waveguide element 24,and light sources 23, 25A, 25B coupled to the waveguide element 24 alongan edge 27 of a primary waveguide surface and at the ends of waveguideextensions 26A, 26B, respectively. Additional light sources (not shown)are contemplated to be coupled to the waveguide element 24 at the end ofwaveguide extensions 26C and 26D, and along edge 28. Waveguideextensions 26A-26D are curved toward a primary plane of the waveguideelement 24, such that the side profile of the resulting system 21 isthinner than it would otherwise be if the extensions 26A-26D werestraight.

FIG. 4 is a schematic perspective view illustration view of an exemplaryLCD system 31 according to one embodiment of the invention. The system31 includes a LCD panel 32, a waveguide element 34, a first light source33 optically coupled to an edge 37 of the waveguide element 34, andadditional light sources 34A-34I optically coupled to the back side 35of the waveguide element 34.

Various embodiments of the invention also provide methods of lighting aLCD panel utilizing light sources as described above. A LED panel may belit by any combination of light sources that provides complete anduniform illumination of the panel. Light may be provided to the panelfrom light sources located along edge or back regions of the waveguideelement, by direct backlighting, or use of any combination of lightsources arranged to emit light directly to a LED panel and/or to emitlight into one or more interposing waveguide elements.

Although the invention has been described with reference to the aboveembodiments, it will be understood that modifications and variations areencompassed within the spirit and scope of the invention. Accordingly,the invention is limited only by the following claims.

What is claimed is:
 1. A liquid crystal display (LCD) system comprising:a) a liquid crystal display panel comprising a viewing area; b) at leastone waveguide element comprising a plurality of light entry regions; c)a first light-emitting source comprising a first plurality of LEDs,wherein the first plurality of LEDs is positioned to emit light into theat least one waveguide element at a first light entry region of theplurality of light entry regions, and wherein the first plurality ofLEDs is arranged along at least one peripheral edge of the at least onewaveguide element and outside the viewing area; and d) a secondlight-emitting source comprising a second plurality of LEDs, wherein thesecond plurality of LEDs is positioned within the viewing area to emitdirect backlight onto the liquid crystal display panel; wherein thefirst light-emitting source and the second light-emitting source arearranged to light different regions of the liquid crystal display panel.2. A liquid crystal display system according to claim 1, wherein the atleast one waveguide element comprises a plurality of waveguide elements,the first light-emitting source is positioned to emit light into atleast one first light entry region of a first waveguide element of theplurality of waveguide elements, and the second light-emitting source ispositioned to emit light into at least one second light entry region ofa second waveguide element of the plurality of waveguide elements.
 3. Aliquid crystal display system according to claim 2, wherein the firstwaveguide element is arranged to light a central or interior region ofthe liquid crystal display panel, and the second waveguide elementarranged to light a peripheral or outer region of the liquid crystaldisplay panel.
 4. A liquid crystal display system according to claim 2,wherein the first waveguide element and the second waveguide element arearranged in a layered configuration.
 5. A liquid crystal display systemaccording to claim 2, wherein the first waveguide element and the secondwaveguide element abut one another laterally.
 6. A liquid crystaldisplay system according to claim 1, wherein the first light entryregion comprises at least one of a top edge of the at least onewaveguide element, a bottom edge of the at least one waveguide element,a first side edge of the at least one waveguide element, and a secondside edge of the at least one waveguide element.
 7. A liquid crystaldisplay system according to claim 1, wherein any of the firstlight-emitting source and the second light-emitting source is embeddedwithin a surface of the at least one waveguide element, or is opticallycoupled to at least one recess defined in a surface of the at least onewaveguide element.
 8. A liquid crystal display system according to claim1, further comprising a third light-emitting source positioned to emitdirect backlight onto the liquid crystal display panel or to emit lightinto the at least one waveguide element.
 9. A liquid crystal displaysystem according to claim 1, wherein the first plurality of lightemitting diodes is arranged in a first strip, and the second pluralityof light emitting diodes is arranged in a second strip.
 10. A liquidcrystal display system according to claim 9, wherein at least one of thefirst strip and the second strip comprises a electrostatic dischargediode in electrical communication with the plurality of light emittingdiodes arranged in the respective strip.
 11. A liquid crystal displaysystem according to claim 1, wherein each of the first plurality oflight emitting diodes and the second plurality of light emitting diodescomprises light emitting diodes adapted to emit wavelengths differingfrom one another.
 12. A liquid crystal display system according to claim1, further comprising a common control circuit in electricalcommunication with the first light emitting source and the second lightemitting source.
 13. A liquid crystal display system according to claim1, wherein the at least one waveguide element defines at least oneopening or gap, and the at least one opening or gap is positioned toallow passage of light from the at least a second light-emitting sourcefor direct backlighting of the liquid crystal display panel withoutpassage of said light through a material of any waveguide element of theat least one waveguide element.
 14. A liquid crystal display systemaccording to claim 1, wherein the at least one waveguide elementcomprises multiple waveguide elements separated by at least one space,and the at least one space is positioned to allow passage of light fromthe at least a second light-emitting source for direct backlighting theliquid crystal display panel without passage of said light through amaterial of any waveguide element of the at least one waveguide element.15. A liquid crystal display system according to claim 1, wherein the atleast one waveguide element consists of a single waveguide elementcomprising a unitary body structure.
 16. A liquid crystal display systemaccording to claim 2, wherein the first waveguide element circumscribesat least a portion of the second waveguide element.
 17. A liquid crystaldisplay system according to claim 2, wherein the first waveguide elementcircumscribes an entirety of the second waveguide element.